From owner-freebsd-current@FreeBSD.ORG Fri May 27 18:16:35 2005 Return-Path: X-Original-To: freebsd-current@FreeBSD.ORG Delivered-To: freebsd-current@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id D1B4416A41C for ; Fri, 27 May 2005 18:16:35 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6B77243D49 for ; Fri, 27 May 2005 18:16:32 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from [192.168.254.14] (imini.samsco.home [192.168.254.14]) (authenticated bits=0) by pooker.samsco.org (8.13.3/8.13.3) with ESMTP id j4RIIKjg050670; Fri, 27 May 2005 12:18:20 -0600 (MDT) (envelope-from scottl@samsco.org) Message-ID: <429763B0.2060705@samsco.org> Date: Fri, 27 May 2005 12:15:12 -0600 From: Scott Long User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.7.7) Gecko/20050416 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Garrett Wollman References: <4295D51F.50106@centtech.com> <429606D9.6080602@cs.tu-berlin.de> <42960ACB.7090801@cs.tu-berlin.de> <42960CFE.4060307@centtech.com> <42960F8F.2050109@samsco.org> <42961195.30608@centtech.com> <429613FB.80100@samsco.org> <42968AD4.3020603@centtech.com> <4296997C.9030700@samsco.org> <20050526235852.M54386@lexi.siliconlandmark.com> <42969C1B.5010301@samsco.org> <17047.25282.72131.519040@khavrinen.csail.mit.edu> In-Reply-To: <17047.25282.72131.519040@khavrinen.csail.mit.edu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.8 required=3.8 tests=ALL_TRUSTED autolearn=failed version=3.0.2 X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on pooker.samsco.org Cc: FreeBSD Current Subject: Re: Disable read/write caching to disk? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 May 2005 18:16:36 -0000 Garrett Wollman wrote: > < said: > > >>is just as much work as porting GFS, if not more, since UFS/FFS is >>closely tied to the buffer cache and block layers on BSD, and divorcing >>probably would be quite difficult. > > > For multiple writers, probably so. For the single-writer case, I > don't think so, since the readers can mount a snapshot while the > writer mounts the read-write view. Well, having a writer is pointless if the readers are stuck on a snapshot. Also, I'm not exactly sure how dirty buffers get flushed to disk in the case of a snapshot. Recall that the snapshot file only save the deltas of the old data, and flushing those deltas to disk is still under the control of the VM/buffer/cache system. You'd probably still have to have some sort of inter-computer synchronization system in place. > > All this would be a lot easier if we had a storage manager more like > ZFS's. > Well, ZFS doesn't really exist yet, so it's hard to draw a comparison ;-) Scott